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Can anyone explain to me the difference between internal relation and foreign key constraint in mysql as found in this image? As i learned the basic database design in Microsoft SQL server management tool, this internal relation concept is new to me, and getting error for foreign key in my Web App. Also if I reverse engineer the database to get a visual schema, no connection between tables is visible if I use only internal relation. Foreign key is needed to generate those connect.

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  • Maybe internal relation is confusing because you are making up the concept :p – Drew Aug 14 '16 at 16:15
  • You should state what your current understanding of a foreign key is. – SPlatten Aug 14 '16 at 16:46
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    Please provide a link to where "internal relation" is defined or used. (I have never heard of it, either.) – Rick James Aug 14 '16 at 16:57
  • I can describe the difference between logical relations, conceptual relationships and physical foreign key constraints, but I've never heard of internal relations. – reaanb Aug 14 '16 at 16:57
  • could not be able to make up something even i tried to :P added an image and a link to a forum post regarding internal relations – adnan88 Aug 14 '16 at 17:10
  • Please [use text, not images/links, for text--including tables & ERDs.](https://meta.stackoverflow.com/q/285551/3404097) Paraphrase or quote from other text. Use images only for what cannot be expressed as text or to augment text. Images cannot be searched for or cut & pasted. Include a legend/key & explanation with an image. Make your post self-contained. – philipxy Aug 09 '19 at 05:38

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This is what you need to read: What are the "Internal Relations" defined in phpMyAdmin?

This is something for MyISAM tables, which don't support foreign keys. It's internal to the phpMyAdmin tool.

For databases like MySQL that do support foreign keys, it's not an adequate substitute. Setting up an internal relation doesn't create foreign keys, and outside of the phpMyAdmin tool, internal relations have no effect.

"Internal relation" is not a general referential database term, as several people have pointed out.

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